Exhaust gas emitted from an internal combustion engine is a heterogeneous mixture that contains gaseous emissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”) as well as condensed phase materials (liquids and solids) that constitute particulate matter. Catalyst compositions typically disposed on catalyst supports or substrates are provided in an engine exhaust system to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components.
Particulate filters remove particulate matter, such as soot, from the exhaust gas by trapping the particulate matter in a filter substrate. Over time, the capacity of the filter substrate is maximized such that the particulate filter must be regenerated using a regeneration system. The regeneration system performs a regeneration operation that increases heat realized by the particulate filter, thereby burning away the trapped particulate matter. Various state government regulations require the regeneration system to pass an emission inspection, which includes diagnosing whether the particulate filter is properly regenerated.